This invention relates to a subsea well completion system for handling oil and/or gas production from multiple offshore wells, and to the components of such a system. In particular, it provides a system, its components, and a method for establishing fluid communication and production capability between multiple template-drilled wells and a production pipeline via a subsea atmospheric manifolding chamber.
This invention relates to the production of hydrocarbon fluids from subaqueous formations utilizing a system of submerged, template-drilled wellheads and a submerged well completion system. Recent developments in the offshore oil and gas industry extend production to undersea areas, such as the outer fringes of the continental shelves and the continental slopes. A submarine production system is believed to be the most practical method of reaching the subaqueous deposits. Although hydrocarbons are the main concern at this time, it is contemplated that subaqueous deposits of sulfur and other minerals can be obtained from beneath the seas. While bottom-supported permanent surface installations have proved to be economically and technologically feasible in comparatively shallow waters, in deeper waters, such as several hundred to several thousand meters, utilization of such surface installations must be limited to very special situations. Installations extending above the water surface are also disadvantageous even in shallower water where there are adverse surface conditions, as in areas where the bottom-supported structure of the above-surface production platforms are subject to ice loading.
Subsea systems are feasible for installing multiple wellheads in relatively close proximity through the use of a drilling template secured on the marine floor. Such systems can be operated from remote, floating surface facilities using electrohydraulic control systems, with the subsea systems being connected to the surface facilities by flowlines for production fluids, injection fluids, hydraulic controls, electric cable, and the like.
Habitable, subsea work enclosures, or satellites, can be maintained adjacent multiple, template-drilled wellheads for housing operating and/or maintenance personnel, as disclosed, for example, in U.S. Pat. No. 3,556,208 (Dean). In such systems, the subsea satellite is independently connected to a number of surrounding subsea wellheads and serves to control the production from, and maintenance of, the wellheads. The wells are drilled in a circular pattern through a template on the marine floor, the template serving also as a base upon which the satellite is installed. The production/control passages of each of the wells are connected to production equipment within the satellite by separate connector units which are independently lowered into place from a surface vessel and form portions of the flow paths between the wellheads and the production equipment within the satellite.
While the aforementioned subsea satellite systems prove generally satisfactory in water depths of about 100 to 150 meters, the use of such systems at depths on the order of 300 to 750 meters presents certain problems. For example, the utilization of guidelines and diver assistance for subsea installation of the components of the system becomes more complex with increasing water depths. In waters of such substantial depth, it becomes necessary to employ dynamic guidance systems, including remote television and/or sonar monitoring, during the installation process. Furthermore, subsea installation of the satellite on the template in prior systems presents problems in terms of guidance of the satellite into proper position on the template and the need to fasten the satellite to the template. Also, prior art subsea well completion systems typically utilize submerged work enclosure hulls having vertically arranged hull penetrators. Such an arrangement of the penetrators produces undesirable hull stress conditions, particularly at depths in excess of 150 meters.
It is an objective of the present invention to overcome the problems and disadvantages of the prior art by providing an improved subsea well completion system, and component parts thereof, capable of simplified, guidelineless installation on the marine floor, as well as an improved subsea satellite installation procedure. It is a further objective of the present invention to provide a subsea well completion system, and components thereof, which will facilitate and insure proper alignment and orientation of the respective components with respect to each other as they are installed on the marine floor. An additional objective is to provide structural protection for the components of the well completion system. It is also an objective of the present invention to provide an improved marine floor base template for guiding marine floor well drilling equipment at multiple wellheads and for supporting and aligning a subsea work-enclosure hull and wellhead connectors.
Additional objectives and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and advantages of the invention will be realized and attained by means of the instrumentalities and combinations, particularly pointed out in the appended claims.
To achieve the objectives and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a subsea well completion system for multiple subsea wells, including a fluid-tight work enclosure hull containing manifold means, the hull having a plurality of radially-disposed lateral penetration means extending therethrough, the penetration means being operatively connected to the manifold means, and a base template having means for securing the template to the marine floor in a substantially horizontal position and having a lower support structure for supporting the work enclosure hull, the template further having an upper guidance structure comprising a plurality of substantially vertical guide members mounted in spaced radial array, each guide member extending inwardly toward the center of the template, forming an opening at the central portion of the template for receiving the work enclosure hull, a portion of the upper peripheral surface of each guide member sloping downwardly toward the opening for guiding the hull as it is lowered during installation of the hull onto the template.
As embodied and broadly described herein, the invention comprises a subsea well completion system for establishing production capability from multiple subsea wells, comprising a fluid-tight work enclosure hull containing manifold means, the hull having a plurality of radially-disposed lateral penetration means extending therethrough, the penetration means being operatively connected to the manifold means and a base template having means for securing the template to the marine floor in a substantially horizontal position and having a lower support structure for supporting the work enclosure hull, the lower support structure of the template includes a plurality of substantially vertical well conductor pipes spaced around the template at a common radial distance from the center of the template for aligning the individual wells during drilling, the upper section of each conductor pipe terminating in a wellhead, the template further having an upper guidance structure comprising a plurality of substantially vertical guide members mounted in spaced radial array, each guide member extending inwardly toward the center of the template forming an opening at the central portion of the template for receiving the work enclosure hull, a portion of the upper peripheral surface of each guide member sloping downwardly toward the opening for guiding the hull as it is lowered during installation of the hull onto the template.
As embodied and broadly described herein, the invention further comprises a subsea system for handling marine well fluids from multiple subsea wells, comprising a fluid-tight work enclosure hull having a plurality of radially-disposed lateral penetration means for releasable fluid connection through the hull, a base template having well bay forming means comprising a plurality of vertical dividers mounted in spaced radial array on the template and extending inwardly from the outer peripheral portion of the template toward the central portion of the template, the upper peripheral surface of each dividing means sloping downwardly toward the central portion of the template for guiding the work enclosure hull as it is lowered during installation onto the template, wellhead connector means installed in a well bay for releasably connecting a wellhead to a penetration means to establish fluid communication therebetween, the wellhead connector means comprising a fluid connection assembly and a rigid, open guide frame surrounding and rigidly secured to the fluid connection assembly, the width of the radially outermost portion of the guide frame, with respect to the central portion of the template, being adapted to prevent lateral and radial inward misorientation of the guide frame and the wellhead connector means as they are moved laterally into the well bay during installation thereof onto the template.
Broadly, a subsea base template for guiding marine floor well drilling equipment at multiple wells and supporting a subsea work enclosure hull and wellheads in accordance with the invention comprises a lower support structure comprising a substantially horizontally aligned, open tubular framework and a plurality of substantially vertical well conductor pipes spaced around the peripheral portion of the framework and integral therewith for aligning the well drilling equipment, the upper section of each well conductor pipe terminating in a wellhead, the central portion of the framework being adapted to support the subsea work enclosure hull and the peripheral portion being adapted to support the wellheads, and an upper guidance structure comprising a plurality of guide members rigidly mounted on, and extending vertically from, the lower support structure in spaced radial array, each guide member extending inwardly toward the center of the template, forming a substantially cylindrical opening at the central portion of the framework for receiving the work enclosure hull, a portion of the upper surface of each guide member sloping downwardly toward the cylindrical opening for guiding the work enclosure hull as it is lowered during installation thereof onto the template, the guide members further providing structural protection for the work enclosure hull and the wellheads.
A subsea base template for guiding marine floor well drilling equipment at multiple wells and supporting a subsea work enclosure hull and wellheads in accordance with the invention also comprises a lower support structure comprising a substantially horizontally aligned, open tubular framework and a plurality of substantially vertical well conductor pipes spaced around the peripheral portion of the framework and integral therewith for aligning the well drilling equipment, the upper section of each well conductor pipe terminating in a wellhead, the central portion of the framework being adapted to support the subsea work enclosure hull and the peripheral portion being adapted to support the wellheads; and an upper guidance structure comprising a plurality of guide members rigidly mounted on, and extending vertically from, the lower support structure in spaced radial array, each guide member extending inwardly toward the center of the template, forming a substantially cylindrical opening at the central portion of the framework for receiving the work enclosure hull, a portion of the upper surface of each guide member sloping downwardly toward the cylindrical opening for guiding the work enclosure hull as it is lowered during installation thereof onto the template the guide members further providing structural protection for the work enclosure hull and the wellheads, wherein the upper guidance structure further comprises blocking means rigidly mounted between each pair of adjacent guide members, except that said blocking means is not mounted between one pair of preselected adjacent guide members to permit receipt between the one pair of guide members of a work enclosure hull alignment means extending laterally from the periphery of the work enclosure hull as the hull is lowered during installation of the hull onto the template, thereby orienting the hull.
The invention further comprises a subsea base template for guiding marine floor well drilling equipment at multiple wells and supporting a subsea work enclosure hull, wellheads, and wellhead connector means, comprising a lower support structure comprising a substantially horizontally aligned, open tubular framework and a plurality of substantially vertical well conductor pipes spaced around the peripheral portion of the framework and integral therewith, for aligning the well drilling equipment, the upper section of each well conductor pipe terminating in a wellhead, the central portion of the framework being adapted to support the subsea work enclosure hull and the peripheral portion being adapted to support the wellheads and wellhead connector means, and an upper guidance structure comprising a plurality of guide members rigidly mounted on, and extending vertically from, the lower support structure in spaced radial array, each guide member extending inwardly toward the center of the template, forming a substantially cylindrical opening at the central portion of the framework for receiving the work enclosure hull, a portion of the upper surface of each guide member sloping downwardly toward the cylindrical opening for guiding the work enclosure hull as it is lowered during installation thereof onto the template, the vertical guide members being situated such that adjacent members define a radially inwardly tapered well bay for each wellhead for funneling the wellhead connector means into place during installation thereof onto the template, the guide members further providing structural protection for the work enclosure hull, the wellheads, and the wellhead connector means.
As embodied and broadly described herein, the invention further comprises a method of establishing production capability from multiple subsea wellheads on a base template secured to the marine floor, comprising: providing a work enclosure hull containing a manifold, the hull having a substantially cylindrical portion with a plurality of radially-disposed lateral hull penetrators extending therethrough and operatively connected to the manifold; providing an upper guidance structure on the template comprising a plurality of substantially vertical guide members mounted in spaced radial array, each guide member extending inwardly from the outer periphery of the template, thereby providing a substantially cylindrical opening at the central portion of the template for receiving the work enclosure hull, and portion of the upper peripheral surface of each guide member sloping downwardly toward the cylindrical opening; lowering the work enclosure hull from a position directly above the template and funneling it through the upper guidance structure into the cylindrical opening at the central portion of the template, the work enclosure hull being guided into its resting position on the template by the guide members; and establishing subsea fluid communication between the subsea wellheads and the work enclosure hull.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention.